TY - JOUR
T1 - The Na+/I- symporter mediates active iodide uptake in the intestine
AU - Nicola, Juan Pablo
AU - Basquin, Cécile
AU - Portulano, Carla
AU - Reyna-Neyra, Andrea
AU - Paroder, Monika
AU - Carrasco, Nancy
PY - 2009/4
Y1 - 2009/4
N2 - Absorption of dietary iodide, presumably in the small intestine, is the first step in iodide (I-) utilization. From the bloodstream, I - is actively taken up via the Na+/I- symporter (NIS) in the thyroid for thyroid hormone biosynthesis and in such other tissues as lactating breast, which supplies I- to the newborn in the milk. The molecular basis for intestinal I- absorption is unknown. We sought to determine whether I- is actively accumulated by enterocytes and, if so, whether this process is mediated by NIS and regulated by I - itself. NIS expression was localized exclusively at the apical surface of rat and mouse enterocytes. In vivo intestine-to-blood transport of pertechnetate, a NIS substrate, was sensitive to the NIS inhibitor perchlorate. Brush border membrane vesicles accumulated I- in a sodium-dependent, perchlorate-sensitive manner with kinetic parameters similar to those of thyroid cells. NIS was expressed in intestinal epithelial cell line 6, and I - uptake in these cells was also kinetically similar to that in thyrocytes. I- downregulated NIS protein expression and its own NIS-mediated transport both in vitro and in vivo. We conclude that NIS is functionally expressed on the apical surface of enterocytes, where it mediates active I- accumulation. Therefore, NIS is a significant and possibly central component of the I- absorption system in the small intestine, a system of key importance for thyroid hormone biosynthesis and thus systemic intermediary metabolism.
AB - Absorption of dietary iodide, presumably in the small intestine, is the first step in iodide (I-) utilization. From the bloodstream, I - is actively taken up via the Na+/I- symporter (NIS) in the thyroid for thyroid hormone biosynthesis and in such other tissues as lactating breast, which supplies I- to the newborn in the milk. The molecular basis for intestinal I- absorption is unknown. We sought to determine whether I- is actively accumulated by enterocytes and, if so, whether this process is mediated by NIS and regulated by I - itself. NIS expression was localized exclusively at the apical surface of rat and mouse enterocytes. In vivo intestine-to-blood transport of pertechnetate, a NIS substrate, was sensitive to the NIS inhibitor perchlorate. Brush border membrane vesicles accumulated I- in a sodium-dependent, perchlorate-sensitive manner with kinetic parameters similar to those of thyroid cells. NIS was expressed in intestinal epithelial cell line 6, and I - uptake in these cells was also kinetically similar to that in thyrocytes. I- downregulated NIS protein expression and its own NIS-mediated transport both in vitro and in vivo. We conclude that NIS is functionally expressed on the apical surface of enterocytes, where it mediates active I- accumulation. Therefore, NIS is a significant and possibly central component of the I- absorption system in the small intestine, a system of key importance for thyroid hormone biosynthesis and thus systemic intermediary metabolism.
KW - Active iodide transport
KW - Dietary iodide absorption
KW - Enterocyte brush border
KW - Sodium/iodide symporter
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U2 - 10.1152/ajpcell.00509.2008
DO - 10.1152/ajpcell.00509.2008
M3 - Article
C2 - 19052257
AN - SCOPUS:65649113307
SN - 0363-6143
VL - 296
SP - C654-C662
JO - American Journal of Physiology - Cell Physiology
JF - American Journal of Physiology - Cell Physiology
IS - 4
ER -